FIG. 1A is a detail from a prior art stator showing overlap of an outer race and a blade assembly prior to engagement of the outer race and the blade assembly.
FIG. 1B is a detail from the prior art stator showing the engagement of the outer race and the blade assembly. The following should be viewed in light of FIGS. 1A and 1B. For a torque converter stator, it is known to join an outer race, for example, race 10, with a portion of a blade assembly, for example, portion 12 which has a smooth circumference or round bore, by forming teeth 14 in the outer race and axially displacing the outer race into portion 12 so that the teeth cut into the portion 12. The preceding procedure results in the teeth cutting into portion 12. Unfortunately, to reduce hoop stresses in portion 12 due to the cutting process, the amount that the teeth cut into portion 12, and therefore the size of the teeth, must be kept to a minimum, which results in reduced torque capacity for the stator as described infra. The preceding procedure results in radially outward force, for example, in direction 16, caused by the cutting/displacing action of the teeth with respect to portion 12. Unfortunately, the force pushes portion 12 radially outward and contributes to hoop stresses in portion 12.
In general, portion 12 is formed of aluminum and teeth 14 are formed of steel. Aluminum has a much greater thermal expansion coefficient than steel and thus under high temperature operating conditions for the stator, portion 12 expands radially outward (in direction 16) faster than the outer race expands radially outward, and “pulls away from” the outer race. As portion 12 pulls away, the teeth are drawn out of portion 12, eventually leaving only tips 18 of the teeth in contact with surface 20 of portion 12 so that only tips 18 and surface 20 connect the blade assembly to the outer race. Prior to the expansion noted above, sides 22 of the blade portion are circumferentially pressing against sides 24 of the teeth to transfer the torque to the outer race and thus, the torque capacity of the stator is relative to the capability of the intermeshed segments 26 and 28 of the outer race and portion 12, respectively, to withstand a circumferential shearing force. Unfortunately, the torque capacity is greatly reduced in the case when only tips 18 and surface 20 connect the blade assembly to the outer race.
Thus, there is a long-felt need for a stator having a higher torque capacity, in particular, under high temperature operating conditions.